class MenuLinkTranslation

class MenuLinkTranslation extends MenuLink {
    use I18nQueryTrait;
    
    /**
     * Drupal 6 table names.
     */
    const I18N_STRING_TABLE = 'i18n_strings';
    
    /**
     * {@inheritdoc}
     */
    public function query() {
        // Ideally, the query would return rows for each language for each menu link
        // with the translations for both the title and description or just the
        // title translation or just the description translation. That query quickly
        // became complex and would be difficult to maintain.
        // Therefore, build a query based on i18nstrings table where each row has
        // the translation for only one property, either title or description. The
        // method prepareRow() is then used to obtain the translation for the other
        // property.
        // The query starts with the same query as menu_link.
        $query = parent::query();
        // Add in the property, which is either title or description. Cast the mlid
        // to text so PostgreSQL can make the join.
        $query->leftJoin(static::I18N_STRING_TABLE, 'i18n', 'CAST([ml].[mlid] AS CHAR(255)) = [i18n].[objectid]');
        $query->addField('i18n', 'lid');
        $query->addField('i18n', 'property');
        // Add in the translation for the property.
        $query->innerJoin('locales_target', 'lt', '[i18n].[lid] = [lt].[lid]');
        $query->addField('lt', 'language');
        $query->addField('lt', 'translation');
        return $query;
    }
    
    /**
     * {@inheritdoc}
     */
    public function prepareRow(Row $row) {
        if (!parent::prepareRow($row)) {
            return FALSE;
        }
        // Save the translation for this property.
        $property_in_row = $row->getSourceProperty('property');
        // Set the i18n string table for use in I18nQueryTrait.
        $this->i18nStringTable = static::I18N_STRING_TABLE;
        // Get the translation for the property not already in the row and save it
        // in the row.
        $property_not_in_row = $property_in_row == 'title' ? 'description' : 'title';
        return $this->getPropertyNotInRowTranslation($row, $property_not_in_row, 'mlid', $this->idMap);
    }
    
    /**
     * {@inheritdoc}
     */
    public function fields() {
        $fields = [
            'language' => $this->t('Language for this menu.'),
            'title_translated' => $this->t('Menu link title translation.'),
            'description_translated' => $this->t('Menu link description translation.'),
        ];
        return parent::fields() + $fields;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getIds() {
        $ids['language']['type'] = 'string';
        return parent::getIds() + $ids;
    }

}